Machines in the semiconductor assembly industry often have a number of electrically driven components, each of which requires an electrical supply in order to operate. These components have different functions, and may well have different requirements as regards voltage, current and/or consistency of power supply. The question of how to optimally supply power to these myriad components is of interest to the industry. An example of such a machine used for semiconductor assembly is an automated die bonding machine, which is used to place semiconductor chips onto a carrier, such as a lead frame or substrate. It has, amongst its components, motors to drive a bond head and to drive a wafer table, optical components for monitoring the die bonding process and logic circuitry to synchronize and manipulate the various components. The power supply system is usually rated in the 600 W to 4 kW range.
According to current practice, each component or set of components is connected to a suitably-rated power supply module that is sufficient to serve the electrical power needs of the components connected to it. Each rated power supply module is a separate device, and each separate module is compartmentalized and preferably stored adjacent each other at a location accessible to the components of the die bonding machine. Each module is designed to be able to supply enough electrical current for all permutations of power requirements. For example, a servomotor requires an initial surge in power input in order to start up the motor before stabilizing at a fairly constant continuous rating level once the load it is driving is moving. A power rating that is sufficient to handle the subsequent constant rating as well as the initial motor surge load is thus necessary to avoid tripping of the power supply during start-up. As a result, there is wastage of capability in having a high power rating to cater for such a type of component or equipment that does not continuously require a high rating. This approach is not cost-effective.
Furthermore, each power supply module is of itself a complete power supply system and takes up space. There is no scalability since each module is designed for a particular rating or maximum power output, and new complete modules have to be added if a higher power rating is required. Thus, there is an inefficient use of resources and there is limited scope to keep costs down while at the same time including redundancy in the system. Moreover, each complete module has to be replaced if it is faulty, which would also tend to increase down-time and costs.
Another problem with using separate power supply modules to serve the machine is that a relatively complex control circuit needs to be implemented, which increases the overall cost of the system. It would thus be desirable to utilize a central power supply that is configurable at a lower cost to supply electrical current to diverse components comprised in a machine.